scripts: Add rustfmt presubmit hook script

A wrapper of rustfmt for configurable source file list and rustfmt binary.

Change-Id: I67a86838bead6736d9b30891b0dcd26476286b3b

preupload-hooks/rustfmt.py

diff --git a/preupload-hooks/rustfmt.py b/preupload-hooks/rustfmt.py
new file mode 100755
index 0000000..e153c36
--- /dev/null
+++ b/preupload-hooks/rustfmt.py
@@ -0,0 +1,73 @@
+#!/usr/bin/env python3
+# Copyright 2022 Google LLC
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Wrapper to run  rustfmt for repo preupload."""
+
+import argparse
+import os
+import subprocess
+import sys
+
+
+def get_parser():
+    """Return a command line parser."""
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--rustfmt_path",
+                        default="rustfmt",
+                        help="The path to the rustfmt binary.")
+    parser.add_argument('files',
+                        type=str,
+                        nargs='*',
+                        help='If specified, only consider rustfmt in '
+                        'these files.')
+    return parser
+
+
+def main(argv):
+    """The main entry."""
+    parser = get_parser()
+    opts = parser.parse_args(argv)
+
+    # Check and set rustfmt path in case `source build/setup.sh` is not run in
+    # the shell session. In repo preupload, the path should be set in
+    # PREUPLOAD.cfg.
+    if opts.rustfmt_path != "rustfmt":
+        # Add rustfmt path to system PATH and set up RUSTUP_HOME at one level up
+        # rustfmt has to have both variables set up to work properly.
+        path = os.path.realpath(opts.rustfmt_path + "/..")
+        os.environ["PATH"] = path + ":" + os.getenv("PATH")
+        os.environ["RUSTUP_HOME"] = path + "/.."
+
+    # Only process .rs files
+    file_list = [f for f in opts.files if f.endswith("rs")]
+    if not file_list:
+        sys.exit(0)
+
+    cmd = [opts.rustfmt_path, "--check", "--color", "never"]
+
+    for f in file_list:
+        cmd.append(f)
+
+    # Run rustfmt on all the .rs files in the file list. `--check` flag
+    # prints out the formatting error and return with exit(1).
+    try:
+        subprocess.run(cmd, check=True)
+    except subprocess.CalledProcessError as e:
+        print(f"rustfmt check failed\ncmd: {cmd}\nexit code {e.returncode}")
+        sys.exit(e.returncode)
+    else:
+        sys.exit(0)
+
+
+if __name__ == '__main__':
+    main(sys.argv[1:])